Immune complement activation is attenuated by surface nanotopography

The immune complement (IC) is a cell-free protein cascade system, and the first part of the innate immune system to recognize foreign objects that enter the body. Elevated activation of the system from, for example, biomaterials or medical devices can result in both local and systemic adverse effects and eventually loss of function or rejection of the biomaterial. Here, the researchers have studied the effect of surface nanotopography on the activation of the IC system. By a simple nonlithographic process, gold nanoparticles with an average size of 58 nm were immobilized on a smooth gold substrate, creating surfaces where a nanostructure is introduced without changing the surface chemistry. The activation of the IC on smooth and nanostructured surfaces was viewed with fluorescence microscopy and quantified with quartz crystal microbalance with dissipation monitoring in human serum. Additionally, the ability of pre-adsorbed human immunoglobulin G (IgG) (a potent activator of the IC) to activate the IC after a change in surface hydrophobicity was studied. It was found that the activation of the IC was significantly attenuated on nanostructured surfaces with nearly a 50% reduction, even after pre-adsorption with IgG. An increase in surface hydrophobicity blunted this effect. The possible role of the curvature of the nanoparticles for the orientation of adsorbed IgG molecules, and how this can affect the subsequent activation of the IC, are discussed. The present findings are important for further understanding of how surface nanotopography affects complex protein adsorption, and for the future development of biomaterials and blood-contacting devices

Adsorption behavior and enzymatically or chemically induced cross-linking of a mussel adhesive protein

The adsorption behavior of the mussel adhesive protein Mytilus edulis foot protein-1 (Mefp-1) has been investigated on a negatively charged polar SiO2 surface and an electrically inert non-polar CH3-terminated thiolated gold surface. How the structure of adsorbed Mefp-1 is changed upon chemically and enzymatically induced cross-linking using sodium periodate (NaIO4) and catechol oxidase, both of which transform DOPA residues in Mefp-1 into highly reactive o-quinones, was also investigated. The results are compared with those resulting from addition of Cu2+ to adsorbed Mefp-1, which forms complexes with and catalyses oxidation of DOPA residues, previously suggested to participate in the cohesive and adhesive properties of the byssus thread of M. edulis. By combining surface plasmon resonance (SPR) and quartz crystal microbalance/dissipation (QCM-D) measurements, the effects of these agents were investigated with respect to changes in the amount of coupled water, the viscoelastic properties (rigidity) and the hydrodynamic thickness of the protein adlayers. The layer of Mefp-1 formed on the bare CH3-terminated surface was elongated, flexible and coupled hydrodynamically a substantial amount of water, whereas Mefp-1 formed a rigidly attached adlayer on the SiO2 surface. Upon enzymatically and chemically induced cross-linking of Mefp-1 formed on the CH3 surface, the rigidity of the adlayer(s) increased significantly. A similar increase in the rigidity was observed also upon addition of Cu2+, suggesting that the high level of metal ions present in the byssus thread might be essential for the cohesive and adhesive properties of this protein. For the mass-uptake kinetics of enzymatically induced cross-linking, three different phases were observed and are interpreted as competition between binding of protein and release of coupled water. For the reaction with NaIO4 and Cu2+ only release of water affected the coupled mass. The importance of this type of information for an improved understanding of the strong adhesion and cohesive properties in marine environments is discussed

A Simple and Efficient Method for Photometric Estimation of the State of Pigment Aggregation in Fish Melanophores : Physiology

Volume: 5Start Page: 959End Page: 96